The present invention relates generally to a pipe switch for use in a conveying unit for pneumatically conveying bulk material.
German Pat. No. 41 14 949 C1 describes a pipe switch including a housing which has an inlet port and two outlet ports, and accommodates a plug for selectively connecting the inlet port with either one of the two outlet ports. The plug exhibits a circumferential perimeter, which is at least partially spherically arched, and is formed therein with a channel. The plug is rotatably supported in the housing about a pivot axis which extends perpendicular to a great circle of a sphere containing the circumferential perimeter. The housing is provided with an inner surface which complements the circumferential perimeter of the plug, with the inlet port and the outlet ports of the housing being connectable via the channel in a substantially smooth manner. The circumferential surface of the plug is a freely-shaped surface area (a random surface area which is characterized by varying radii of curvature), which constitutes only by approximation and sacrifice of an accurate coincidence of the ports of the channel in the plug with corresponding ports in the housing an area of a spherical segment which is bounded by two parallel planes oriented in symmetry to a center plane extending perpendicular to the pivot axis of the plug. The axis of the channel is offset with respect to the pivot axis of the plug while the channel itself is in symmetric disposition to the center plane. In order to allow assembly and dismantling of the plug, the housing is split in the center plane. Thus, the joint lies on a great circle in the rotational area of the plug and must be made with particular care. Even then, the seals typically used in this area are subject to increased wear during rotation of the plug.